Information used by a processor is often stored in a memory system that includes a storage device and a cache memory. The processor will request information that is retrieved either from the cache memory or the storage device. The cache memory stores much less information than the storage device, but has a much shorter latency than the storage device. Latency is the time between initiating a request for information in a memory system and the moment the information is retrieved. The read operation is faster when there is a lower latency.
Retrieving the information directly from the cache memory substantially reduces latency for the processor. When the processor runs a particular software application, input/output (I/O) patterns in the information used by the processor tend to repeat. There is a good chance that information obtained from the storage device will be retrieved again. The cache memory stores information most recently accessed by the processor. When the processor requests information that is in the cache memory, the slower storage device does not need to be accessed and the information is retrieved directly from the faster cache memory. The cache memory reduces the number of times that information is retrieved from the storage device. The cache memory improves the performance of the memory system by reducing an average latency for information requested by the processor.